Maximum precision for quantifiable success.Reference materials and other accredited calibration gas mixtures.

→ Accredited calibration gas mixtures

It’s now official: Linde sets standards.

Linde has a lot of accredited laboratories according to ISO 17025 in many countries. This was followed in 2009 by accreditation as a producer of reference materials to ISO Guide 34 in Europe and Asia, and in 2013 in the USA. Linde is now literally setting standards for the calibration of gas measuring instruments and is the first gas supplier in the German-speaking world able to produce gas mixtures covering all metrological hierarchies. This means that, as an industrial enterprise, we are making a key contribution to the metrological infrastructure worldwide.

02 Accredited calibration gas mixtures

In an age of global trade, analytical measuring results have to be comparable. This requirement is meanwhile satisfied by a large number of international directives and standards, e.g. DIN EN ISO/IEC 17025¹. Such regulations call for the metrological traceability of measuring results using certified reference materials as the basis for comparability. Traceability is the possibility of verifying measuring results through calibration with measuring instruments of a known accuracy which are linked to acknowledged measurement standards. In the world of physical metrology, such standard measures are the internationally recognised

Linde quality hierarchy for calibration gas mixtures.

embodiment of the relevant SI units. These principles form the basis for the analytical results of test and calibration laboratories. Linde calibration gas mixtures are distinguished according to the degree of accuracy required. The mixtures are produced in coordinated levels of manufacturing tolerance, measurement uncertainty and traceability. Highly optimised production processes and analysis methods allow us to offer mixtures that accurately match customer requirements in terms of precision while satisfying all definitive norms.

Reference materialsAccreditation as manufacturer of reference materials

Mixtures with DAkkS calibration certificateAccreditation as a calibration laboratory

Standard gas mixtures: class 1QM – Linde Gas certification

• Directly traceable to SI base unit (kg)• Analytical verification against

internationally accepted standards• Relative measurement uncertainty ≈ 0.5%

• Traceable to internationally accepted standards (BAM, NMi, NPL, etc.)

• Relative measurement uncertainty ≈ 1%

• Traceable to Internal Linde standards (PEH mixture)

• Relative measurement uncertainty ≥ 2 %

Calibration gas mixtures from Linde Metrological properties

ISO Guide 34

ISO 17025

ISO 9001

¹ DIN EN ISO/IEC 17025 “General requirements for the competence of testing & calibration laboratories”

03Accredited calibration gas mixtures

Reference materials.

ISO Guide 34² defines reference materials as mixtures of substances with an extremely precise composition, which are linked to the International System of Units (SI) by complete metrological traceability and a specified level of measurement uncertainty. Reference materials used for the calibration of measuring instruments form an essential part of analytical chemistry. Our reference materials have been developed for customers with exacting requirements in terms of measurement uncertainty and traceability. The determination of reference values is based on the international standards ISO 6142 “Gas analysis – Preparation of calibration gas mixtures – Gravimetric method” and ISO 6143 “Gas analysis – Comparison methods for determining and checking the composition of calibration gas mixtures”. Preparation of the mixtures involves determining the amount of each component by means of gravimetric analysis. The high-precision sets of masses used here are periodically calibrated by approved calibration laboratories. Our reference materials are thus directly traceable to the SI base unit of the kilogram. The accuracy achievable with the gravimetric method significantly depends on the purity of the parent gas used to produce the mixtures. For Linde reference materials we therefore only use high purity base gases and compressed gas containers, which have undergone first-class pretreatment. After filling, the gravimetrically prepared mixtures are homogenised and verified by means of analysis. The calibration gases used for such analysis are themselves traceable to gas mixtures of the national metrology institutes BAM³, NPL⁴ and VSL (NMi)⁵. Analytical verification is subject to stringent requirements, which are described in detail in ISO 6143 and ISO Guide 35⁶. The calculation of the measurement uncertainty for the certified values complies with the recommendations of GUM (ISO/IEC Guide 98-3: 2008 “Guide to the Expression of Uncertainty in Measurement”). Linde has developed and validated a software program called “HiQ calc” for this

purpose and it forms one of the cornerstones of our accreditation as a producer of reference materials.

Linde reference materials offer users major benefits:• International comparability at the highest level• Short delivery times• Simple order processing via Linde delivery service

² ISO Guide 34 “General requirements for the competence of reference material producers” ³ BAM: Federal Institute for Materials Research and Testing (Germany) ⁴ NPL: National Physical Laboratory (UK) ⁵ VSL (NMi): Dutch Metrology Institute (Netherlands)⁶ ISO Guide 35 “Reference materials – General & statistical prinicples for certification”

04 Accredited calibration gas mixtures

Typical certificate for a reference material

0,000

0,020

0,040

0,060

0,080

0,100

0,120

0,140

0,160

0 200 0 250 0 300 0,350 0,400 0,450[10-6,, mol/ mol CO

,,CC 2]

±2s

xm

Substance amount fractionaction

DAkk

scan

dida

t eCRMCRM

CRMCRM

BAM NP

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DAkks

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DAkkS

Calibration gas mixtures with accreditation certificate.

Official stipulations are prompting customers to increasingly make the award of contracts conditional on accreditation as a calibration laboratory. Calibration performed by calibration laboratories offers users certainty as regards the reliability of measuring results, improves competitive ability on national and international markets and serves as a metrological basis for monitoring measuring instruments and test equipment in the framework of quality assurance. International accreditation bodies have confirmed that our accredited calibration laboratories in many countries, e.g. Germany and United Kingdom, meet the stringent requirements of DIN EN ISO/IEC 17025. Accreditation in Germany is carried out by the Deutsche Akkeditierungs-stelle (DAkkS) Accreditation Body and in Switzerland by the Swiss Calibration Service (SCS). BOC Limited, a member of The Linde Group in the UK, also has accreditation from the United Kingdom Accreditation Service (UKAS) to ISO Guide 34 as a Reference Materials Producer and ISO/IEC 17025 as a Calibration Laboratory for a wide range of calibration gas mixtures. Our accredited calibration mixtures are traceable to internationally recognised reference materials of BAM, NPL and VSL (NMi) and our own reference materials. Our accreditations include calibration for binary and multicomponent mixtures, as well as calibration gases for emissions testing, calorific value measuring instruments and process gas chromatographs. These mixtures are preferably filled into 10 and 40 litre aluminium cylinders.

Procedure for analysis and certification for calibration accredited mixtures

All key metrological data can be found on the calibration certificate:• measurement method• conditions of measurement• result with uncertainty• traceability

Certified reference materials Measuring instrument, calibration curve, DAkkS candidate

Measuring result and uncertainty

Gas mixture

The key customer benefits of accredited calibration are:• International validity of measured values determined• High standing of accreditations in many countries

both inside and outside Europe• Evidence of traceability, in particular for accredited testing laboratories

x = 10.3 ± 0.1 ppm CO₂ expansion factor k=2 calibration procedure

conditions

05Accredited calibration gas mixtures

DAkkS calibration certificate

Excerpt from Linde’s delivery programme.

Reference materials (DAKKS, ISO Guide 34)

Binary mixtures Mixtures for emissions  testingSynthetic natural  gas mixtures

Measured variableCOCO₂CH₄C₂H₆C3H8

NOO₂SO₂NO₂CO, CO₂, C₃H₈, O₂

C₂–C₆, CO₂, CO, O₂, N₂, H₂, He

Amount fraction5 ppm–10 %5 ppm–30 %5 ppm–50 %10 ppm–5 %5 ppm–5 %5 ppm–1 %5 ppm–25 %5–1000 ppm5–1000 ppmVarying

Varying

MatrixN₂, Synthetic Air*N₂, Synthetic AirN₂, Synthetic Air*N₂, CH₄N₂, CH₄N₂N₂N2, Synthetic Air*Synthetic AirN₂

CH₄

Relative uncertainty (%)0.5–0.80.5–0.80.5–0.80.5–0.80.5–0.80.5–0.80.5–0.80.81.00.5–0.8

0.5–1.0

NB *Only outside flammable limits

Calibration laboratory (DAKKS, ISO 17025)

Binary and/or ternary mixtures

Quaternary and  pentanary mixtures

Synthetic mixtures of  natural gas

Measured variableHe **CO **CO₂ **CH₄ **C₃H₈ **NO **O₂ **SO₂ **NO₂ **NH3

C6H14

H2

CO, CO₂, C₃H₈CO, SO₂, NOCO, CO₂, C₃H₈, O₂C2–C6, CO2, CO, O2, N2, H2, He

Amount fraction1%-50%5 ppm–10 %5 ppm–30 %5 ppm–50 %5 ppm–5 %5 ppm–1 %5 ppm–30 %1–5000 ppm5–1000 ppm5–500 ppm5–500 ppm1–20 %VaryingVaryingVaryingVarying

MatrixN₂, Synthetic AirN₂, Synthetic Air*N₂, Synthetic AirN₂, Synthetic Air*N₂, CH₄N₂N₂N₂Synthetic AirN₂N₂, Synthetic AirN₂N₂N₂N₂CH4

Relative uncertainty (%)1.01.01.01.01.01.01.01.02.02.02.01.01.01.01.01.0–2.0

NB * Only outside flammable limits ** two of these components can be used in ternary mixtures

06 Accredited calibration gas mixtures

07Accredited calibration gas mixtures

Linde as a qualified supplier of environmental gas standards.

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Getting ahead through innovation.

With its innovative concepts, Linde is playing a pioneering role in the global market. As a technology leader, it is our task to constantly raise the bar. Traditionally driven by entrepreneurship, we are working steadily on new high-quality products and innovative processes. Linde offers more. We create added value, clearly discernible competitive advantages and greater profitability. Each concept is tailored specifically to meet our customers’ requirements – offering standardised as well as customised solutions. This applies to all industries and all companies regardless of their size. If you want to keep pace with tomorrow’s competition, you need a partner by your side for whom top quality, process optimisation and enhanced productivity are part of daily business. However, we define partnership not merely as being there for you but being with you. After all, joint activities form the core of commercial success.

Linde – ideas become solutions.

Linde AGGases Division, Seitnerstrasse 70, 82049 Pullach, Germany Phone +49.89.7446-1661, Fax +49.89.7446-2071, hiq@linde-gas.com, http://hiq.linde-gas.com

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